Wear-resistant compacts comprising superabrasive (i.e., superhard) material are utilized for a variety of applications and in a corresponding variety of mechanical systems. For example, wear resistant superabrasive elements are used in drilling tools (e.g., inserts, cutting elements, gage trimmers, etc.), machining equipment, bearing apparatuses, wire drawing machinery, and in other mechanical systems.
In one particular example, polycrystalline diamond compacts have found particular utility as cutting elements in drill bits (e.g., roller cone drill bits and fixed cutter drill bits) and as bearing surfaces in so-called “thrust-bearing” apparatuses. A polycrystalline diamond compact (“PDC”) cutting element or cutter typically includes a diamond layer or table formed by a sintering process employing high-temperature and high-pressure conditions that causes the diamond table to become bonded to a substrate (e.g., a cemented tungsten carbide substrate), as described in greater detail below.
When a polycrystalline diamond compact is used as a cutting element, it may be mounted to a drill bit either by press-fitting, brazing, or otherwise coupling the cutting element into a receptacle defined by the drill bit, or by brazing the substrate of the cutting element directly into a preformed pocket, socket, or other receptacle formed in the drill bit. In one example, cutter pockets may be formed in the face of a matrix-type bit comprising tungsten carbide particles that are infiltrated or cast with a binder (e.g., a copper-based binder), as known in the art. Such drill bits are typically used for rock drilling, machining of wear resistant materials, and other operations which require high abrasion resistance or wear resistance. Generally, a rotary drill bit may include a plurality of polycrystalline abrasive cutting elements affixed to a drill bit body.
A PDC (as well as other superhard materials) may be fabricated by placing a layer of diamond crystals or grains adjacent one surface of a substrate and exposing the diamond grains and substrate to an ultra-high pressure and ultra-high temperature (“HPHT”) process. Thus, a substrate and adjacent diamond crystal layer may be sintered under ultra-high temperature and ultra-high pressure conditions to cause the diamond crystals or grains to bond to one another. In addition, as known in the art, a catalyst may be employed for facilitating formation of polycrystalline diamond. In one example, a so-called “solvent catalyst” may be employed for facilitating the formation of polycrystalline diamond. For example, cobalt, nickel, and iron are among examples of solvent catalysts for forming polycrystalline diamond. In one configuration, during sintering, solvent catalyst from the substrate body (e.g., cobalt from a cobalt-cemented tungsten carbide substrate) becomes liquid and sweeps from the region behind the substrate surface next to the diamond powder and into the diamond grains. Of course, a solvent catalyst may be mixed with the diamond powder prior to sintering, if desired.
Also, as known in the art, such a solvent catalyst may dissolve carbon at high temperatures. Such carbon may be dissolved from the diamond grains or portions of the diamond grains that graphitize due to the high temperatures of sintering. When the solvent catalyst is cooled, at least a portion of the carbon held in solution may precipitate or otherwise be expelled from the solvent catalyst and may facilitate formation of diamond bonds between adjacent or abutting diamond grains. Thus, the diamond grains become mutually bonded to form a polycrystalline diamond table upon the substrate. The solvent catalyst may remain in the diamond layer within the interstitial space between the diamond grains or the solvent catalyst may be at least partially removed and optionally replaced by another material, as known in the art. For instance, the solvent catalyst may be at least partially removed from the polycrystalline diamond by acid leaching. One example of a conventional process for forming polycrystalline diamond compacts is disclosed in U.S. Pat. No. 3,745,623 to Wentorf, Jr. et al., the disclosure of which is incorporated herein, in its entirety, by this reference.
Superhard materials (other than polycrystalline diamond) may also be formed by HPHT processing (i.e., sintering) or may be formed by other processes (e.g., chemical vapor deposition or any other suitable process), without limitation.
It may be appreciated that it would be advantageous to provide methods for forming superabrasive materials and apparatuses, structures, or articles of manufacture including such superabrasive material.